Absolute fastest way to grind out HO-229?

I’m a regular WT hater, but there are three things this game does that no other can do:

Flight model Damage model Flying Wing

These are the only three things I care about. I only downloaded the game so I could buy a premium HO-229 and have fun, but that does not appear to be an option. Until there is though, I will grind and buy my way through the game like everyone else. What is the fastest way to do this? I have disposable income so money is no object. What is the absolute fastest way to acquire the HO-229?

Currently I’ve been boom-n-zooming the HE-100 because I don’t like slow planes in arcade and get roughly two kills per round and that nets me on average 700ish RP. Is there any better way to go about this?